The present invention involves a process of coating a non-woven fiber glass mat with foam or froth on the same wet process line used to make the mat, as an intermediate step in the mat manufacturing process, and the foam coated fiber glass mat products that result. These coated mats have many uses, but are especially useful as a facing on a gypsum wallboard for exterior application and on which stucco is applied.
Fibrous non-woven mats are often formed into a wet mat from an aqueous dispersion of fibers such as glass and/or synthetic organic fibers can include other fibers such as cellulose fibers, ceramic fibers, etc. and can also include particles of inorganic material and/or plastics. Usually a solution of urea formaldehyde resin, usually modified with a thermoplastic polymer, or one of many other known resin binders is applied to a the wet non-woven web of fibers and then, after removing excess binder and water, the bindered web is dried and heated further to cure the urea formaldehyde resin or other resin binder to form a non-woven mat product. A typical process is disclosed in U.S. Pat. Nos. 4,112,174 and 3,766,003, the disclosures of which are hereby incorporated herein by reference.
The fiber glass mat (Johns Manville""s 7502 Matxe2x80x942 lb./100 sq. ft.) made using a binder of urea formaldehyde performed good in the process disclosed in U.S. Pat. No. 4,647,496 to make a faced insulating gypsum board, also disclosed in that patent, but the mat was not as strong as desired which caused process breakouts adding to production costs. This mat was also more rigid than desired which made it difficult to fold around the edges of the board and also irritated the hands and arms of the workers handling and installing the insulating board product. Further, when the faced insulated gypsum board was cut, the dust from the mat was excessive and further irritated those it contacted, particularly if the workers bare arms, etc. were sweaty and exposed to the dust. Skin abrasion and irritation was also a problem for those handling the mat and the faced board when not wearing gloves and long sleeve shirts.
To address the inadequate strength problem a small portion of polyester, polyethylene terathalate (PET), fibers were used in place of an equal amount of glass fibers and the urea formaldehyde resin binder was replaced with an acrylic binder containing a small amount of a stearylated melamine. This improved the strength adequately and also improved the handling characteristics of the mat somewhat, i.e. the mat is more friendly to those handling and installing the mat or board, but the acrylic bound mat is more expensive and less fire (flame) resistant. Such mats are disclosed in U.S. Pat. No. 5,772,846. While the mats disclosed by this latter reference have substantially improved xe2x80x9chandxe2x80x9d and cause very little abrasion or discomfort in handling, the cost is higher, the mat is less flame resistant than the mat disclosed in U.S. Pat. No. 4,647,496 and further improvement is still desired by some users.
There still exists a need for a nonwoven fiber glass mat that has better flame resistance, lower cost and good handlability (flexibility and non abrasive/non irritating to the skin).
It is an object of the present invention to provide a foam or froth coated nonwoven fibrous mat useful as a facer on gypsum insulating board of the type described in U.S. Pat. No. 4,647,496 having one or more of improved handling characteristics, improved flame resistance, improved flexibility and product that produces less, or less irritating, dust when the faced gypsum board is cut than the mats used heretofore for facing insulating gypsum board.
It is a further object of the present invention to provide flexible mats containing a major portion of less expensive chopped glass fibers that can be used for facing gypsum wall board and other products.
It is a further object to provide a low cost method of making a foam faced fibrous non-woven mat on a wet process line without having to coat a dried mat either in-line or off-line and without having to dry the mat a second time.
The present invention includes a method of making a foam coated fibrous non-woven mat where the fibers are preferably, but not necessarily, bonded together with a conventional mat binder comprising using a wet process to form a wet non-woven web from a low concentration aqueous slurry followed by partially dewatering the mat, preferably, but not necessarily, adding an excess of aqueous resin binder, removing some but not all of the binder, then applying an aqueous foam or froth having a high air content and a high blow ratio, onto the top of the wet mat in-line, and then heating the mat to remove the water, and preferably to cure the binder, and set the foam coating. The aqueous foam slurry contains a foam that breaks down fairly quickly such that the mat has enough permeability to allow drying air to penetrate the mat. The foam coating will hold the non-woven fibrous web together adequately for some applications, but it is preferred to use a conventional binder in a conventional manner to give the non-woven finished mat greater strength. The aqueous foam is foam having a blow ratio of at least 15, preferably at least 25, and most preferably between 15 and 30, a viscosity of at least 200 centipoise, preferably at least 500 centipoise, and have rapid heat breaking and non-draining characteristics.
The present invention also includes the mats made by the above process, or a different process wherein foam is applied to wet mat in-line, comprising a non-woven fibrous mat with the fibers bound together with a resinous binder and having a dry foam coating on one surface of the mat, the dry foam coating preferably being permeable to allow the mat to breathe and to allow later coatings to penetrate the foam coating. The foam layer may penetrate into the non-woven fibrous mat a distance that is a small fraction of the total thickness of the mat. This mat is very useful as a facer for many products, particularly gypsum wallboard and insulating boards of various kinds. The foam coating ties up the fibers preventing loose fibers from or fiber ends from getting on people handling and/or installing the product faced with the foam coated mat and causing irritation and/or itching. The foam forming the foam coating on the mat can contain fire retardant or intumescent material, adhesives, colorants and/or other materials for changing the appearance or performance of the mat surface.
The present invention also includes laminates comprising a base layer such as gypsum wallboard or insulating boards, fiberglass blanket, plywood or other wood product having adhered thereto a foam coated fibrous non-woven mat as described above.
Preferably the inventive mat for facing the insulating gypsum board has a basis weight within the range of about 1.5 and about 3, preferably within the range of about 1.8-2.5 pounds per 100 square feet, most preferably about 2.2-2.4 pounds per 100 sq. ft. Preferably the binder content of the dried and cured mats is within the range of about 15 wt. percent and about 25 wt. percent, most preferably about 20-25 wt. percent, based on the weight of the finished mat. Preferably the inventive mat contains a major portion of glass fibers, but can also contain a minor portion of polymer fibers, such as PET polyester fibers, cellulosic fibers like wood pulp, and ceramic fibers, bound together with a minor portion of a conventional modified urea formaldehyde binder. Other conventional binders can be used instead of the modified UF binder such as a phenolic resin, a melamine formaldehyde, a furfuryl alcohol, a latex containing a mixture of a cross linked vinyl chloride acrylate copolymer having a glass transition temperature as high as about 113 degrees F., preferably about 97 degrees F., and a small amount of a stearylated melamine and other conventional mat binders.
When the word xe2x80x9caboutxe2x80x9d is used herein it is meant that the amount or condition it modifies can vary some beyond that so long as the advantages of the invention are realized. Practically, there is rarely the time or resources available to very precisely determine the limits of all the parameters of ones invention because to do would require an effort far greater than can be justified at the time the invention is being developed to a commercial reality. The skilled artisan understands this and expects that the disclosed results of the invention might extend, at least somewhat, beyond one or more of the limits disclosed. Later, having the benefit of the inventors disclosure and understanding the inventive concept and embodiments disclosed including the best mode known to the inventor, the inventor and others can, without inventive effort, explore beyond the limits disclosed to determine if the invention is realized beyond those limits and, when embodiments are found to be without any unexpected characteristics, those embodiments are within the meaning of the term about as used herein. It is not difficult for the artisan or others to determine whether such an embodiment is either as expected or, because of either a break in the continuity of results or one or more features that are significantly better than reported by the inventor, is surprising and thus an unobvious teaching leading to a further advance in the art.